Charge amplifier with high-resolution sensitivity setting

Abstract

The utility model discloses a charge amplifier with high resolution and sensitivity setting. The charge amplifier comprises a charge conversion circuit, a high-pass filter circuit and a sensitivity setting circuit which are connected in sequence. The charge conversion circuit converts charge signals output by the piezoelectric sensor into voltage signals, the high-pass filter filters out low-frequency drift signals existing in the signals, and the sensitivity setting circuit comprises two digital potentiometers and an operational amplifier. The single-chip microcomputer controls the two digital potentiometers to set the resistance values of the digital potentiometers so as to realize matching of the piezoelectric sensors with different sensitivities. According to the utility model, the sensitivity setting is more accurate, the problem that the amplification factor of the sensitivity setting circuit cannot be accurately matched with the sensitivity of the piezoelectric sensor is solved, the sensitivity setting range of the charge amplifier is improved, and the charge amplifier can be matched with the piezoelectric sensor with lower sensitivity and the piezoelectric sensor with higher sensitivity; therefore, the charge amplifier has better universality, and the cost is greatly saved.

Description

Technical Field

[0001] The utility model relates to the technical field of charge amplifiers, and particularly relates to a charge amplifier with a high-resolution sensitivity setting. Background Art

[0002] In most cases, non-electrical quantities are mainly to be measured. Non-electrical quantities such as physical quantities and mechanical quantities are converted into electrical quantities with corresponding relationships through sensor technology and electromagnetic methods, and then can be made into data that can be processed, calculated, and analyzed through the conversion of secondary instruments. Piezoelectric sensors can convert pressure signals into electrical signals through piezoelectric crystals. They have excellent dynamic response characteristics, as well as characteristics such as wide frequency band, low power consumption, high sensitivity, strong structure, and stable operation, making them an important part of measuring force, acceleration, torque, and vibration signals. And the charge amplifier, as a device that converts the charge signal output by the piezoelectric sensor into a voltage signal, needs to ensure that the charge signal is accurately amplified without generating excessive errors.

[0003] In the prior art, the accuracy of the sensitivity setting of the charge amplifier is low, and it cannot be accurately matched with the sensitivity of the piezoelectric sensor, resulting in a large error in the output signal after amplification, affecting the subsequent analysis and calculation of the signal, and the matching range of the sensitivity of the piezoelectric sensor is limited, and it cannot adapt to piezoelectric sensors with small sensitivities and large sensitivities at the same time. Summary of the Utility Model

[0004] The utility model provides a charge amplifier with a high-resolution sensitivity setting to solve the problems that the sensitivity setting of the charge amplifier cannot be accurately matched with the piezoelectric sensor and the charge amplifier cannot adapt to piezoelectric sensors with small sensitivities and large sensitivities at the same time.

[0005] Specifically, the utility model proposes a charge amplifier with a high-resolution sensitivity setting. The charge amplifier with a high-resolution sensitivity setting includes a charge conversion circuit, a high-pass filter circuit, and a sensitivity setting circuit;

[0006] Among them, the charge conversion circuit is used to receive the charge signal output by the piezoelectric sensor. The input end of the high-pass filter circuit is connected to the output end of the charge conversion circuit to filter out the low-frequency drift signal in the signal. The input end of the sensitivity setting circuit is connected to the output end of the high-pass filter circuit and is used to set the sensitivity of the charge amplifier;

[0007] The sensitivity setting circuit includes an operational amplifier U3, a digital potentiometer U4, and a digital potentiometer U5;

[0008] The digital potentiometers U4 and U5 are digital potentiometers AD5259; the pin 2 of the digital potentiometer U4 is connected to the output terminal of the high-pass filter circuit, the pin 3 is connected to the inverting input terminal of the operational amplifier U3, the pin 1 is connected to VDD, the pin 4 is connected to VSS, the pin 6 is grounded, the pin 7 is connected to VDD, and the pins 8 and 9 are connected to the control chip;

[0009] The non-inverting terminal of the operational amplifier U3 is grounded;

[0010] The pin 2 of the digital potentiometer U5 is connected to the inverting input terminal of the operational amplifier U3, the pin 3 is connected to the output terminal of the operational amplifier U3, the pin 1 is connected to VDD, the pin 4 is connected to VSS, the pin 6 is grounded, the pin 7 is connected to VDD, and the pins 8 and 9 are connected to the control chip.

[0011] Further, the charge conversion circuit includes an operational amplifier U1, a feedback capacitor Cf, a feedback resistor Rf, a capacitor C1, and a resistor R1. The inverting input terminal of the operational amplifier U1 is connected to the output signal of the piezoelectric sensor. The capacitor C1 is connected in parallel between the inverting input terminal and the output terminal of the operational amplifier U1. The resistor R1 is connected in series with the output terminal of the operational amplifier U1. The resistor R1 is connected to the input terminal of the high-pass filter circuit. The feedback capacitor Cf and the feedback resistor Rf are both connected in parallel across the two ends of the series circuit composed of the operational amplifier U1 and the resistor R1; among them, the operational amplifier U1 is connected to its inverting input terminal, and the non-inverting input terminal of the operational amplifier U1 is grounded.

[0012] Further, the high-pass filter circuit includes an operational amplifier U2, a capacitor C2, a capacitor C3, a resistor R2, and a resistor R3. The capacitor C2 is connected in series with the charge conversion circuit. One end of the capacitor C3 is connected in series with the capacitor C2, and the other end is connected to the non-inverting input terminal of the operational amplifier U2. One end of the resistor R3 is connected between the capacitor C3 and the non-inverting input terminal of the operational amplifier U2, and the other end is grounded. One end of the resistor R3 is connected between the capacitor C2 and the capacitor C3, and the other end is connected to the inverting input terminal of the operational amplifier U2. The inverting input terminal of the operational amplifier U2 is connected to its output terminal. The output terminal of the operational amplifier U2 is connected to the sensitivity setting circuit.

[0013] Further, the sensitivity setting circuit further includes a capacitor C4, a capacitor C5, a capacitor C6, a capacitor C7, a capacitor C8, a capacitor C9, a capacitor C10, a capacitor C11, a capacitor C12, a capacitor C13, a resistor R6, a resistor R7, a resistor R8, and a resistor R9;

[0014] Pin 1 of the digital potentiometer U4 is connected to capacitors C4, C5 and pin 10, and the other ends of capacitors C4 and C5 are grounded. Pin 4 is connected to capacitors C7 and C8, and the other ends of capacitors C7 and C8 are grounded. Pins 8 and 9 are pulled up to VDD through resistors R6 and R7 respectively. Capacitor C6 is connected in parallel between pins 4 and 5 of the digital potentiometer U4;

[0015] Pin 1 of the digital potentiometer U5 is connected to capacitors C9, C10 and pin 10, and the other ends of capacitors C9 and C10 are grounded. Pin 4 is connected to capacitors C12 and C13, and the other ends of capacitors C12 and C13 are grounded. Pins 8 and 9 are pulled up to VDD through resistors R8 and R9 respectively. Capacitor C11 is connected in parallel between pins 4 and 5 of the digital potentiometer U5.

[0016] The beneficial effects achieved by the present utility model are:

[0017] The charge conversion circuit provided by the utility model is used to receive the charge signal output by the piezoelectric sensor and convert the charge signal into a voltage signal. The high-pass filter circuit is used to filter out the low-frequency drift in the signal. The sensitivity setting circuit is used to set the sensitivity of the charge amplifier. The control chip controls two digital potentiometers to achieve more accurate setting of the sensitivity, greatly reducing the error caused by the insufficient accuracy of the sensitivity setting circuit, and improving the matching range of the charge amplifier for piezoelectric sensors with different sensitivity levels, making the charge amplifier have better versatility. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 FIG. is the circuit schematic diagram of a charge amplifier with high-resolution sensitivity setting provided by the present utility model;

[0019] Figure 2 FIG. is the circuit schematic diagram of the charge conversion circuit in a charge amplifier with high-resolution sensitivity setting provided by the present utility model;

[0020] Figure 3 FIG. is the circuit schematic diagram of the high-pass filter circuit in a charge amplifier with high-resolution sensitivity setting provided by the present utility model;

[0021] Figure 4 FIG. is the circuit schematic diagram of the sensitivity setting circuit in a charge amplifier with high-resolution sensitivity setting provided by the present utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The technical solutions of the present utility model will be described in more detail below with reference to the accompanying drawings. The present utility model includes but is not limited to the following embodiments.

[0023] In order to more clearly understand the above-mentioned objects, features, and advantages of the present utility model, the present utility model will be further described in detail below in conjunction with the accompanying drawings and specific embodiments in the embodiments.

[0024] As shown in the attached Figure 1 figures, a charge amplifier with a high-resolution sensitivity setting of the present utility model includes: a charge conversion circuit 1, a high-pass filter circuit 2, and a sensitivity setting circuit 3;

[0025] As shown in the attached Figure 2 figures, the charge conversion circuit 1 includes an operational amplifier U1, a feedback capacitor Cf, a feedback resistor Rf, a capacitor C1, and a resistor R1; the inverting input terminal of the operational amplifier U1 is connected to the output signal of the piezoelectric sensor, the capacitor C1 is connected in parallel between the inverting input terminal and the output terminal of the operational amplifier U1, the resistor R1 is connected in series with the output terminal of the operational amplifier U1, and both the feedback capacitor Cf and the feedback resistor Rf are connected in parallel across the two ends of the series circuit composed of the operational amplifier U1 and the resistor R1. Among them, the operational amplifier U1 is connected to its inverting input terminal, and the non-inverting input terminal of the operational amplifier U1 is grounded.

[0026] As shown in the attached Figure 3 figures, the high-pass filter circuit includes an operational amplifier U2, a capacitor C2, a capacitor C3, a resistor R2, and a resistor R3; the capacitor C2 is connected in series with the charge conversion circuit 1, one end of the capacitor C3 is connected in series with the capacitor C2, and the other end is connected to the non-inverting input terminal of the operational amplifier U2; one end of the resistor R2 is connected between the capacitor C3 and the non-inverting input terminal of the operational amplifier U2, and the other end is grounded. One end of the resistor R3 is connected between the capacitor C2 and the capacitor C3, and the other end is connected to the inverting input terminal of the operational amplifier U2. The inverting input terminal of the operational amplifier U2 is connected to its output terminal.

[0027] As shown in the attached Figure 4 figures, the sensitivity setting circuit includes an operational amplifier U3, a digital potentiometer U4, a digital potentiometer U5, a capacitor C4, a capacitor C5, a capacitor C6, a capacitor C7, a capacitor C8, a capacitor C9, a capacitor C10, a capacitor C11, a capacitor C12, a capacitor C13, a resistor R6, a resistor R7, a resistor R8, and a resistor R9.

[0028] Pin 2 of the digital potentiometer U4 is connected to the output terminal of the high-pass filter circuit 2, pin 3 is connected to the inverting input terminal of the operational amplifier U3, pin 1 is connected to VDD, capacitor C4, capacitor C5 and pin 10, and the other ends of capacitor C4 and capacitor C5 are grounded, pin 4 is connected to capacitor C7, capacitor C8 and VSS, and the other ends of capacitor C7 and capacitor C8 are grounded, pin 6 is grounded, pin 7 is connected to VDD, pins 8 and 9 are connected to the control chip and are pulled up to VDD through resistor R6 and resistor R7 respectively, capacitor C6 is connected in parallel between pin 4 and pin 5 of the digital potentiometer U4, and the non-inverting terminal of the operational amplifier U3 is grounded.

[0029] Pin 2 of the digital potentiometer U5 is connected to the inverting input terminal of the operational amplifier U3, pin 3 is connected to the output terminal of the operational amplifier U3, pin 1 is connected to VDD, capacitor C9, capacitor C10 and pin 10, and the other ends of capacitor C9 and capacitor C10 are grounded, pin 4 is connected to capacitor C12, capacitor C13 and VSS, and the other ends of capacitor C12 and capacitor C13 are grounded, pin 6 is grounded, pin 7 is connected to VDD, pins 8 and 9 are connected to the control chip and are pulled up to VDD through resistor R8 and resistor R9 respectively, capacitor C11 is connected in parallel between pin 4 and pin 5 of the digital potentiometer U5.

[0030] The input terminal of the charge conversion circuit 1 is connected to the piezoelectric sensor, which is used to receive the charge signal output by the piezoelectric sensor. The charge signal is converted into a voltage signal by the charge conversion circuit 1. The high-pass filter circuit 2 filters out the low-frequency drift signal in the voltage signal to reduce the influence of zero drift on the signal. The sensitivity setting circuit 3 performs normalization amplification on the output signal so that the charge amplifier can adapt to piezoelectric sensors with different sensitivities.

[0031] When the amplification factor of the charge amplifier is relatively large, the low-frequency drift and noise coupled in the signal will also be amplified along with the signal, resulting in unstable output signals. The frequency of the low-frequency drift is mainly distributed in 0 - 100 mHz and does not coincide with the frequency of the signal. Therefore, setting the lower cut-off frequency of the high-pass filter to 250 mHz can effectively filter out the low-frequency drift, reduce the influence of zero drift on the signal, and will not filter out the effective information in the signal;

[0032] The calculation formula for the lower cut-off frequency of the high-pass filter provided by the embodiment of the present application is:

[0033]

[0034] Taking the digital potentiometer AD5259 as an example, two digital potentiometers U4 and U5 cooperate with the operational amplifier U3 to complete the setting of the sensitivity. The control chip controls pins 8 and 9 of the digital potentiometer through I2C communication to change the resistance value of the digital potentiometer. There is a variable resistor between pins 2 and 3 of the digital potentiometer. Pins 1 and 4 of the digital potentiometer are connected to the power supply, pin 6 is grounded, and pin 10 is for address setting;

[0035] Among them, when the digital potentiometers U4 and U5 select a resistance value of 10 kΩ, the number of taps is 256, the supply voltage of the operational amplifier U3 is ±10 V, and the feedback capacitor Cf is 1000 pf, the set output pressure range is 0 - 100 bar. The sensitivity range that the sensitivity setting circuit can set is 0.3906 pC / bar - 25600 pC / bar, and the accuracy of the sensitivity setting circuit is 0.3906 pC / bar. When the set output pressure range is 0 - 200 bar, the sensitivity range that the sensitivity setting circuit can set is 0.1953 pC / bar - 12800 pC / bar, and the accuracy of the sensitivity setting circuit is 0.1953 pC / bar.

[0036] It can be seen from the above that the sensitivity setting circuit provided in this embodiment can enable the charge amplifier to obtain higher accuracy during normalized amplification, and can match piezoelectric sensors with lower sensitivity and piezoelectric sensors with higher sensitivity, featuring high accuracy and strong versatility.

[0037] The parts not detailed in the present utility model are prior art.

[0038] The present utility model is not limited to the above specific embodiments. Those of ordinary skill in the art can implement the present utility model in many other specific embodiments according to the embodiments and the disclosed content of the drawings. Therefore, any design that adopts the design structure and idea of the present utility model and makes some simple transformations or modifications falls within the protection scope of the present utility model.

Claims

1. A charge amplifier with a high-resolution sensitivity setting, characterized in that, The charge amplifier with a high-resolution sensitivity setting includes a charge conversion circuit (1), a high-pass filter circuit (2), and a sensitivity setting circuit (3); Among them, the charge conversion circuit (1) is used to receive the charge signal output by the piezoelectric sensor. The input end of the high-pass filter circuit (2) is connected to the output end of the charge conversion circuit (1) to filter out the low-frequency drift signal in the signal. The input end of the sensitivity setting circuit (3) is connected to the output end of the high-pass filter circuit (2) and is used to set the sensitivity of the charge amplifier; The sensitivity setting circuit (3) includes an operational amplifier U3, a digital potentiometer U4, and a digital potentiometer U5; The digital potentiometer U4 and the digital potentiometer U5 are digital potentiometers AD5259. The pin 2 of the digital potentiometer U4 is connected to the output end of the high-pass filter circuit (2), the pin 3 is connected to the inverting input end of the operational amplifier U3, the pin 1 is connected to VDD, the pin 4 is connected to VSS, the pin 6 is grounded, the pin 7 is connected to VDD, and the pins 8 and 9 are connected to the control chip; The non-inverting input end of the operational amplifier U3 is grounded; The pin 2 of the digital potentiometer U5 is connected to the inverting input end of the operational amplifier U3, the pin 3 is connected to the output end of the operational amplifier U3, the pin 1 is connected to VDD, the pin 4 is connected to VSS, the pin 6 is grounded, the pin 7 is connected to VDD, and the pins 8 and 9 are connected to the control chip.

2. The charge amplifier with a high-resolution sensitivity setting according to claim 1, characterized in that, The charge conversion circuit (1) includes an operational amplifier U1, a feedback capacitor Cf, a feedback resistor Rf, a capacitor C1, and a resistor R1. The inverting input end of the operational amplifier U1 is connected to the output signal of the piezoelectric sensor. The capacitor C1 is connected in parallel between the inverting input end and the output end of the operational amplifier U1. The resistor R1 is connected in series with the output end of the operational amplifier U1. The resistor R1 is connected to the input end of the high-pass filter circuit (2). The feedback capacitor Cf and the feedback resistor Rf are both connected in parallel at both ends of the series circuit composed of the operational amplifier U1 and the resistor R1. Among them, the operational amplifier U1 is connected to its inverting input end, and the non-inverting input end of the operational amplifier U1 is grounded.

3. The charge amplifier with a high-resolution sensitivity setting according to claim 1, characterized in that The high-pass filter circuit (2) includes an operational amplifier U2, a capacitor C2, a capacitor C3, a resistor R2, and a resistor R3. The capacitor C2 is connected in series with the charge conversion circuit (1). One end of the capacitor C3 is connected in series with the capacitor C2, and the other end is connected to the non-inverting input end of the operational amplifier U2. One end of the resistor R3 is connected between the capacitor C3 and the non-inverting input end of the operational amplifier U2, and the other end is grounded. One end of the resistor R3 is connected between the capacitor C2 and the capacitor C3, and the other end is connected to the inverting input end of the operational amplifier U2. The inverting input end of the operational amplifier U2 is connected to its output end. The output end of the operational amplifier U2 is connected to the sensitivity setting circuit (3).

4. The charge amplifier with a high-resolution sensitivity setting according to claim 1, characterized in that The sensitivity setting circuit (3) further includes a capacitor C4, a capacitor C5, a capacitor C6, a capacitor C7, a capacitor C8, a capacitor C9, a capacitor C10, a capacitor C11, a capacitor C12, a capacitor C13, a resistor R6, a resistor R7, a resistor R8, and a resistor R9; Pin 1 of the digital potentiometer U4 is connected to capacitor C4, capacitor C5 and pin 10, and the other ends of capacitor C4 and capacitor C5 are grounded. Pin 4 is connected to capacitor C7 and capacitor C8, and the other ends of capacitor C7 and capacitor C8 are grounded. Pins 8 and 9 are pulled up to VDD through resistor R6 and resistor R7 respectively. Capacitor C6 is connected in parallel between pin 4 and pin 5 of the digital potentiometer U4; Pin 1 of the digital potentiometer U5 is connected to capacitor C9, capacitor C10 and pin 10, and the other ends of capacitor C9 and capacitor C10 are grounded. Pin 4 is connected to capacitor C12 and capacitor C13, and the other ends of capacitor C12 and capacitor C13 are grounded. Pins 8 and 9 are pulled up to VDD through resistor R8 and resistor R9 respectively. Capacitor C11 is connected in parallel between pin 4 and pin 5 of the digital potentiometer U5.

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